Abstract
A piston slap is one of the main vibration sources of the reciprocating machinery. Much work has been done in this field, most of which was based on a constant rotating speed. However, in practice, the speed of a crankshaft may always fluctuate due to the uneven load or excitation. The inertia forces of moving components are much different at the fluctuating rotating speed comparing with that at a constant speed. In this paper, the piston slap and the induced vibration are analyzed based on the instantaneous angular speed measured on a single‐cylinder reciprocating compressor. Firstly, the dynamics of a crank‐connecting rod mechanism is analyzed based on the measured instantaneous angular speed which contains the torsional vibration of the air compressor. The time histories of piston slap impact forces considering and without considering torsional vibration are compared. Then, in order to correlate the piston slap impact with the slap‐induced vibration, the corresponding transfer functions between the middle stroke of the outer surface of the cylinder liner and the excitation points are measured. And the excitation force on the main bearing is also taken into account to bring the simulation closer to the experimental results. The effects of a torsional vibration on the vibration of the cylinder liner are analyzed, and the simulation results show that the torsional vibration is a factor that must be taken into account in the vibration analysis of the single‐cylinder reciprocating compressor.
Highlights
A piston slap, the impact caused by the sidewise motions of pistons across the cylinder clearance spaces, has long been recognized to be a major source of noise and vibration in reciprocating machinery
Ungar and Ross attempt to estimate the vibration and noise power levels induced by the piston slap for the first time [1]. e piston slap at TDC has been simulated by Haddad and Fortescue in an analogue computer [2], and the effects of oil film on piston slap excitation were considered in his following studies [3]
At the beginning of this paper, the instantaneous angular speed is measured on a single-cylinder reciprocating compressor whose medium-low-frequency vibration is mainly concentrated in 100–350 Hz
Summary
A piston slap, the impact caused by the sidewise motions of pistons across the cylinder clearance spaces, has long been recognized to be a major source of noise and vibration in reciprocating machinery. At the beginning of this paper, the instantaneous angular speed is measured on a single-cylinder reciprocating compressor whose medium-low-frequency vibration is mainly concentrated in 100–350 Hz. Based on the instantaneous angular speed, the dynamics of the crank-connecting rod mechanism is analyzed. E time histories of piston slap impact forces considering and without considering torsional vibration are compared. E piston side-thrust force is derived from the forces and moment of the crankshaft, connecting rod, and piston It can be deduced from the equations of the system as shown below: Velocity (m/s) Acceleration (m/s2). E inertial force of the piston slap and connecting rod fluctuate greatly because of the nonzero rotational acceleration of the crankshaft.
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